INVESTIGATION OF LEACHING PROCESSES OF HERBICIDES IN SOIL COLUMN SIMULATING BY HYDRUS-1D MODEL

Piyanuch  Jaikaew; Farag  Malhat; Le  Hoang Tu; Julien  Boulange; Charoen  Jiraratchwaro; Hirozumi  Watanabe

Authors

Piyanuch Jaikaew Department of Civil and Environmental Engineering, Faculty of Science and Engineering, Kasetsart University, Chalermphrakiat Sakon Nakhon Province campus, Sakon Nakhon, 47000, Thailand.
Farag Malhat Department of Pesticide Residues and Environmental Pollution, Central Agricultural Pesticide Laboratory, Agriculture Research Center, Giza, Egypt.
Le Hoang Tu Department of International Environmental and Agricultural Science, Tokyo University of Agricultural and Technology, Fuchu, Tokyo, 183-0054, Japan.
Julien Boulange School of Agriculture, Meiji University, Kawasaki, Japan.
Charoen Jiraratchwaro Department of International Environmental and Agricultural Science, Tokyo University of Agricultural and Technology, Fuchu, Tokyo, 183-0054, Japan.
Hirozumi Watanabe Department of International Environmental and Agricultural Science, Tokyo University of Agricultural and Technology, Fuchu, Tokyo, 183-0054, Japan.

Keywords:

Leaching processes, soil column, HYDRUS-1D, agricultural soil, herbicides

Abstract

leaching experiment focusing on atrazine and metolachlor was conducted using a soil column with prescribed hydrological conditions. The transport parameters determined the concentrations in the soil depth. Atrazine and metolachlor were applied at the surface of the soil column at the average concentrations of 2.23±0.04 and 2.15±0.02 mg kg- 1, for atrazine and metolachlor, respectively. At the end of the experiment, the concentrations of atrazine and metolachlor in the soil surface were 0.0068±0.0015 and 0.0013±0.0012 mgkg-1, respectively. The concentrations in atrazine and metolachlor in the water percolating at the bottom of the column were 0.14±0.03 mg kg-1 and 0.21±0.01 mg kg-1, respectively.The computed dissipation rate constants ranged from 0.014 to 0.036 day-1 for atrazine and from 0.010 to 0.028 day-1 for metolachlor. The corresponding half-lives were 23.5 days and24.7 days for atrazine and metolachlor, respectively. There were no significant differences in leaching nor in the dissipation behaviors between atrazine and metolachlor (Student’ st-test, α = 0.05). The HYDRUS-1D simulated herbicide concentrations had fair accuracy, and the RMSE values between the simulated results and observed data were about 0.25mg.L-1 for atrazine and 0.29 mg.L-1 for metolachlor. At the middle of the soil column, thesoil water concentrations increased to maximum values of 2.24 and 2.98 mg. L-1 at 28 and24 min and decreased to 0.31 and 0.36 mg.L-1 at the final time for atrazine and metolachlor.

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